This invention relates to nitrile polymers stabilized against color degradation caused by ionizing radiation. More particularly, this invention involves the stabilization of nitrile polymers against such discoloration by inclusion of an effective amount of a sulfur containing stabilizer and a sulfur containing plasticizer.
In recent years it has been discovered that certain nitrile polymers having a high proportionate amount of olefinic nitrile component are especially suitable for packaging, test tubes, syringes and other applications particularly because of their excellent water and oxygen barrier properties. However, such nitrile polymers have a tendency to discolor particularly when subject to ionizing radiation used in treating articles made from such nitrile polymers. While a variety of compounds and particularly phenol compounds and triazine compounds such as disclosed in U.S. Pat. No. 3,202,681 and 4,046,735 have been generally known to be useful as stabilizers for various organic compositions, many of such stabilizers are not particularly useful for stabilizing nitrile polymers against color degradation caused by ionizing radiation, e.g. alpha, beta, gamma and electron beam radiation.
Thus, there exists in the art a need for an improved nitrile polymer which is stabilized against color degradation caused by ionizing radiation. This need is provided by the present invention wherein selected sulfur containing compounds are added to the nitrile resin composition.